Engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art, may exhaust a complex mixture of air pollutants. The air pollutants may be gaseous (e.g., CO, NOx, etc.) and may also include solid material, such as particulate matter. Particulate matter may include ash and unburned carbon particles and may sometimes be referred to as soot.
Due to increased environmental concerns, exhaust emission standards have become more stringent. The amount of particulate matter and gaseous pollutants emitted from an engine may be regulated according to the type, size, and/or class of engine. In order to meet these emissions standards, engine manufacturers have pursued improvements in several different engine technologies, such as fuel injection, engine management, and air induction. In addition, engine manufacturers have developed devices and systems for treatment of engine exhaust after it leaves the engine.
Such systems are often referred to as “after-treatment” systems. After-treatment systems may include after-treatment components, such as catalytic converters and particulate traps. For various reasons, owners and/or operators of engine-operated equipment having after-treatment components sometimes remove or bypass the after-treatment components. This however, can result in the equipment producing more exhaust pollutants than it was designed to and/or producing more pollutants than allowed by government emissions regulations.
The Environmental Protection Agency (“EPA”) has mandated that operators of on-highway vehicles must be notified when certain emissions requirements are not met during normal operation of their vehicle. Accordingly, in order to help ensure compliance with emissions regulations such as this and other mandates, it may be advantageous to provide engines with an after-treatment systems with the capability of detecting the presence of after-treatment components and generating a fault if a monitored component is determined to be missing from the system. Moreover, having an on-board diagnostics system may be advantageous for identifying issues early on and hence prevent further costly repairs at a later stage. Systems have been contemplated with such a capability. For example, in SAE technical paper no. 2005-01-3603 entitled Selective Catalytic Reduction On-Board Diagnostics: Past and Future Challenges, Nebergall et al. describe a concept of monitoring for a missing selective catalytic reduction (SCR) catalyst by determining an absolute difference between temperatures upstream of the SCR catalyst and temperatures downstream of the SCR catalyst. There are, however, many operating conditions where upstream temperature and downstream temperature are substantially the same. Nebergall et al. do not disclose any additional conditions for generating a fault indicative of a missing SCR catalyst. Such unrestricted monitoring for temperature differences can produce false positives (i.e., faults generated even though the SCR catalyst is, in fact, present).
The present disclosure is directed at improvements in detecting after-treatment components.